This invention relates to a device enabling the proportioning and dispensing, on a repetitive basis, of all types of powdered products to be packaged in a single or multi-constituent container.
More specifically, the invention is directed to a proportioning dispenser used to proportion and dispense powdered products as part of a packaging machine which itself operates on a repetitive automatic basis, in other words, designed to automatically fill a series of containers appearing sequentially at one or more filling stations in a large-scale process-type operation.
An even more specific focus of the invention is the technical field involving the loading of powders into hollow cylinders or shells to make explosive cartridges.
The type of loading just mentioned has been achieved in the past using a number of different devices, generally involving the principle of overfilling, consisting in discharging into the container a quantity of powder greater than the container's actual capacity. This operation is followed by a wiping off of the surplus product in order to limit the charge to a plane passing through the open top of the container.
A major drawback of this approach is that it leads to considerable pollution of the environment around the machine by the surplus powder which has been wiped off and which is difficult to fully recover by automatic means.
Attempts to deal with this problem in the prior art have involved proportioning the product in advance, particularly by using sliding compartment proportioning devices comprising one or more chambers each feeding a common receiver. The sliding compartment, or each sliding compartment, is moved relative to a template or gauge designed to equalize the load of useful volume and remove the surplus product. The loaded compartment is then discharged into the container.
Such a device cannot provide continuous service and consistent output because the product being proportioned is compressed when passing through the gauge which results in dose variations in a measured quantity or dose that are all the more significant for the smallness of the initial dose.
Moreover, forcing the filled slide into the gauge/template can result in rubbing and heating as well as compression of particles caught between the relatively sliding walls. This can create a fire or explosion in the case of processing inflammable or explosive powders.
Another disadvantage of the above-mentioned solution results from the fact that powdered products are frequently abrasive and cause wear of the slide valve and/or the template. Consequently, the proportioning action becomes unreliable over time, entailing serious repercussions, especially when one must fill a given volume with several powders requiring relatively precise proportioning.
Another prior art solution consists in providing a proportioning device based on filling a scoop by dipping it into a store of the products, then wiping off the surplus with a doctor blade applying against the upper edge of the scoop. This approach provides correct proportioning, but satisfactory dispensing of the products still must be accomplished.
All the design alternatives provided hereto entail the retention of an undetermined amount of powdered products on their walls. As a result, the loads actually dispensed deviate from the load initially required in a completely random manner, depending on whether the walls retain some of the particles from the dispensed loads or, on the other hand, suddenly deliver, as the result of a vibration or impact, all of the various particles that have built up on their walls over previous operating cycles.
A further disadvantage of the solutions offered to data stems from the fact that the devices provided fail to prevent the spreading of a fire resulting from a flaming up or sudden explosion at some point in the transfer chain. They thus constitute a serious hazard in terms of the propagation of a fire which could result in the firing or explosion of the main powder store.